Differential imaging system and preparation method

Abstract

The invention relates to a differential imaging system, comprising a point light source for emitting light; the imaging unit is arranged on the light emitting side of the point light source and is used for receiving and transmitting the light to an imaging surface; the intensity filtering unit is arranged on the conjugate surface of the point light source relative to the imaging unit, the intensity filtering unit has set function type amplitude and is used for performing differential modulation on the light output by the imaging unit to obtain a modulated light field, and the modulated light field forms a differential imaging light field on the imaging surface. The invention also relates to a preparation method of the differential imaging system. The device has the advantages that the intensity filtering unit with the set function type amplitude is arranged on the conjugate face of the point light source relative to the imaging unit, the differential imaging effect can be achieved in the one-time imaging process, the device can be directly integrated in a microscope system, and the light path is simple.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a differential imaging system and a preparation method thereof. Background Art

[0002] The characteristic information of an object is often concentrated at its edges, corresponding to regions with large amplitude or phase gradients in the mathematical representation of the object's light field. Using spatial filtering techniques to differentiate the light field function allows for the extraction of arbitrary or specific edges of the input object, enabling quantitative calculation of light field edges.

[0003] In the existing technology, the mainstream method for achieving mechanical differential imaging is based on the 4f system and requires a pair of confocal Fourier lenses. Its optical path is large and complex, relying on multiple lenses to complete the filtering in coordination. At the same time, it has strict plane wave incidence requirements for the light source and is incompatible with common microscope imaging systems. Summary of the Invention

[0004] The technical problem to be solved by the embodiments of the present invention is to provide a differential imaging system and a preparation method, in which an intensity filter unit with a set functional amplitude is placed on a conjugate plane of a point light source relative to an imaging unit, so as to achieve a differential imaging effect in a single imaging process. The system can be directly integrated into a microscope system with a simple optical path.

[0005] In order to solve the above technical problems, the present invention provides a differential imaging system, comprising: Point light source, used to emit light; An imaging unit, provided on the light-emitting side of the point light source, for receiving and transmitting the light to an imaging surface; An intensity filtering unit is provided on a conjugate plane of the point light source relative to the imaging unit. The intensity filtering unit has a set functional amplitude and is used to differentially modulate the light output by the imaging unit to obtain a modulated light field. The modulated light field forms a differential imaging light field on the imaging plane.

[0006] In a feasible implementation, the intensity filter unit is a filter with a linear function amplitude, and the modulated light field is represented by the following expression: ; in, represents an arbitrary constant; 、 represent the spatial frequency components of the light in Fourier space respectively; represents the Fourier transform result of the light; represents Fourier transform; represents the first-order partial derivative of the light in the x direction.

[0007] In a feasible implementation, the intensity filter unit is a filter with a quadratic function amplitude, and the modulated light field is represented by the following expression: ; in, represents an arbitrary constant; represents the sum of the squares of spatial frequencies; represents the Fourier transform result of the light; represents Fourier transform; represents the Laplacian of the ray.

[0008] In a feasible implementation, the expression of the differential imaging light field is: ; in, represents the differential imaging light field; represents Fourier transform; represents the amplitude transmission function of the intensity filter unit; represents the light incident on the imaging unit; Indicates the secondary phase that does not affect the imaging results; represents the radial coordinate of the imaging plane; represents the distance from the image side principal plane in the imaging unit to the imaging surface; Represents the distance from the image principal plane in the imaging unit to the intensity filtering unit.

[0009] In a feasible implementation, the imaging unit includes a lens, an objective lens, or an optical imaging device based on the conjugate imaging principle.

[0010] In a feasible implementation, the conjugate condition between the plane where the point light source is located and the plane where the intensity filtering unit is located is expressed by the following expression: ; in, represents the distance from the point light source to the principal plane of the image side in the imaging unit; represents the distance from the main plane of the image side in the imaging unit to the intensity filtering unit; represents the focal length of the imaging unit.

[0011] In a feasible implementation, the conjugate condition between the imaging plane and the object plane where the sample is located is expressed by the following expression: ; in, represents the distance from the object plane to the principal plane of the image side in the imaging unit; represents the distance from the image side principal plane in the imaging unit to the imaging surface; represents the focal length of the imaging unit.

[0012] In a feasible implementation, it further includes a light intensity capturing unit, configured to capture the modulated light field after being filtered by the intensity filtering unit.

[0013] In a feasible implementation, the light intensity capturing unit includes a charge coupled device sensor or a complementary metal oxide semiconductor sensor.

[0014] Accordingly, the present invention also provides a method for preparing a differential imaging system, comprising: Provide a point light source for emitting light; Providing an imaging unit, which is arranged on the light-emitting side of the point light source and is used to propagate the light to an imaging surface; An intensity filtering unit is provided and arranged on a conjugate plane of the point light source relative to the imaging unit. The intensity filtering unit has a set amplitude transmission function and is used to differentially modulate the light output by the imaging unit to obtain a modulated light field. The modulated light field forms a differential imaging light field on the imaging plane.

[0015] The implementation of the present invention has the following beneficial effects: Placing an intensity filter unit with a set functional amplitude on the conjugate surface of the point light source relative to the imaging unit can achieve a differential imaging effect in a single imaging process. It can be directly integrated into the microscope system with a simple optical path.

[0016] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a differential imaging system of the present invention; Figure 2 is a light field distribution diagram of an input object in the simulation calculation of the present invention; Figure 3 Schematic diagram of the first-order differential imaging result of the present invention; Figure 4 is a schematic diagram of the relative intensity along the dotted line in the first-order differential imaging result of the present invention; Figure 5 Schematic diagram of the second-order differential imaging result of the present invention; Figure 6 is a schematic diagram of the relative intensity along the dotted line in the second-order differential imaging result of the present invention; Figure 7 It is a step diagram of the differential imaging system preparation method of the present invention. DETAILED DESCRIPTION

[0018] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0019] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] Although methods based on micro-nano optics (such as optical metasurfaces and photonic crystals) can achieve direct Fourier space modulation, they require extremely high processing precision and the resulting high cost, which also limits large-scale applications.

[0022] The present invention provides a differential imaging system, referring to Figure 1 ,include, Point light source 110, for emitting light; The imaging unit 130 is provided on the light-emitting side of the point light source 110 and is used to receive and transmit the light to the imaging surface 150; The intensity filter unit 140 is disposed on a conjugate plane of the point light source 110 relative to the imaging unit 130. The intensity filter unit 140 has a set functional amplitude for differentially modulating the light output by the imaging unit 130 to obtain a modulated light field. The modulated light field forms a differential imaging light field on the imaging plane 150.

[0023] Specifically, the present invention provides a differential imaging system, in which an intensity filter unit 140 is arranged on a conjugate plane of a point light source 110 relative to an imaging unit 130. By utilizing a single imaging unit 130 in combination with an intensity filter unit 140 having a specific functional amplitude, the system effectively solves the above-mentioned defects without requiring the complex optical path of a 4f system and high-precision processing of micro-nano structures. The system has a wide range of applications, can achieve a differential imaging effect in a single imaging process, can be directly integrated into a microscope system, and has a simple optical path.

[0024] In a feasible implementation, the intensity filter unit 140 is a filter with a linear function amplitude, and the modulated light field is represented by the following expression: ; in, represents an arbitrary constant; 、 They represent the spatial frequency components of light in Fourier space respectively; Represents the Fourier transform result of light; represents Fourier transform; Represents the first-order partial derivative of the light in the x direction.

[0025] Specifically, the intensity filter unit 140 uses a filter with an amplitude transmission function of α|x| or α|y|, and is placed on the conjugate plane of the point light source 110 relative to the imaging unit 130. The paraxial spherical wave emitted by the point light source 110 passes through the sample and propagates through the imaging unit 130 to the filter to complete the Fourier transform. The filter modulates the light field in Fourier space to satisfy the above relationship. The linear function amplitude filter corresponds to the first-order differential operation in Fourier space, by screening the high-frequency components in a specific direction ( or ), only retaining the edge information in that direction, thereby achieving directional edge detection. This does not require the dual-lens architecture of the 4f system, and can be accomplished through a single imaging unit 130, simplifying the optical path. After first-order differential imaging, the final result after a Fourier transform is an inverted image with a prominent edge.

[0026] In a feasible implementation, the intensity filter unit 140 is a filter with a quadratic function amplitude, and the modulated light field is represented by the following expression: ; in, represents an arbitrary constant; represents the sum of the squares of spatial frequencies; Represents the Fourier transform result of light; represents Fourier transform; Represents the Laplacian operator of a ray.

[0027] Specifically, the amplitude transmission function is adopted as The filter is placed on the conjugate surface of the point light source 110. After the light from the point light source 110 passes through the sample and the imaging unit 130, it completes the Fourier transform at the filter. The filter modulates the light field according to the above relationship, and finally forms an omnidirectional second-order differential imaging on the imaging surface 150. The quadratic function amplitude filter corresponds to the second-order differential operation (Laplace transform) in Fourier space, and the high-frequency components ( ) is modulated to retain the gradient change areas in all directions, realizing omnidirectional edge detection while avoiding the high-precision processing requirements of micro-nano structures. This can be achieved through conventional filters. After second-order differential imaging, it undergoes another Fourier transform and the final result is an inverted image with highlighted edges.

[0028] In a feasible implementation, the expression of the differential imaging light field is: ; in, represents the differential imaging light field; represents Fourier transform; represents the amplitude transmission function of the intensity filtering unit 140; represents the light incident on the imaging unit 130; Indicates the secondary phase that does not affect the imaging results; represents the radial coordinate of the imaging surface 150; represents the distance from the image side principal plane in the imaging unit 130 to the imaging surface 150; represents the distance from the image-side principal plane in the imaging unit 130 to the intensity filtering unit 140 .

[0029] In a feasible implementation, the imaging unit 130 includes a lens, an objective lens, or an optical imaging device based on the conjugate imaging principle.

[0030] Specifically, the imaging unit 130 includes a single lens, an objective lens, or any optical imaging device based on the conjugate imaging principle. Optical imaging devices based on the conjugate imaging principle (such as telecentric lenses and imaging lens groups) can be adapted to different types of optical systems, broadening the application scenarios of edge enhancement technology.

[0031] In a feasible implementation, the conjugate condition between the plane where the point light source 110 is located and the plane where the intensity filtering unit 140 is located is expressed by the following expression: ; in, represents the distance from the point light source 110 to the principal plane of the image side in the imaging unit 130; represents the distance from the main plane of the image plane in the imaging unit 130 to the intensity filtering unit 140; represents the focal length of the imaging unit 130; The conjugate condition between the imaging plane 150 and the object plane 120 where the sample is located is expressed by the following expression, ; in, represents the distance from the object plane 120 to the principal plane of the image side in the imaging unit 130; represents the distance from the image side principal plane in the imaging unit 130 to the imaging surface 150; represents the focal length of the imaging unit 130 .

[0032] Specifically, the conjugate condition ensures that the light field completes an accurate Fourier transform in the filtering plane, allowing the filter to act accurately in the spatial frequency domain, while ensuring that the imaging plane 150 is conjugated with the sample, ultimately obtaining a clear differential image, solving the incompatibility problem between the 4f system and the microscope, and improving the versatility of the system.

[0033] In a feasible implementation, it further includes a light intensity capture unit for capturing the modulated light field filtered by the intensity filter unit 140; The light intensity capturing unit includes a charge coupled device sensor (CCD) or a complementary metal oxide semiconductor sensor (CMOS).

[0034] Specifically, a CCD or CMOS sensor is set on the imaging surface 150 to capture the intensity distribution of the differential imaging light field modulated by the intensity filtering unit 140 and directly output a digital image to achieve real-time recording of the differential imaging for subsequent analysis.

[0035] The noise level of CCD is usually lower than that of CMOS, which is suitable for scenarios with high signal-to-noise ratio requirements (such as medical microscopic diagnosis). It can reduce the interference of noise on edge positioning and ensure the accuracy of edge enhancement effect.

[0036] Complementary metal oxide semiconductors (CMOS) can simultaneously process both bright and dim light areas, avoiding distortion in the contrast between bright edges and dark backgrounds in edge-enhanced light fields. For example, when light intensity varies significantly around the edges of a sample, CMOS effectively preserves edge detail across the entire image. CMOS sensors consume significantly less power than CCDs, making them suitable for portable devices (such as field inspection microscopes). Furthermore, they can integrate signal processing circuitry, simplifying system design and reducing hardware costs.

[0037] In one embodiment, a Kohler illumination light source is used instead of the point light source 110 and is placed at an infinite distance. The spherical wave is irradiated onto the sample. The sample is an English letter A, such as Figure 2 As shown. Since the Köhler illumination light source is located at an infinite distance, the intensity filter unit 140 can be placed on the conjugate plane according to the conjugate condition formula between the plane where the light source is located and the intensity filter unit 140. The distance between the sample and the main plane of the imaging unit 130 is for , the focal length of the imaging unit 130 is Therefore, according to the conjugate condition formula between the imaging plane 150 and the object plane 120 where the sample is located, the distance between the imaging plane 150 and the main plane of the imaging unit 130 is for , so its magnification is about 1.11 times. First, we can calculate the imaging result of the first-order differential. Taking into account the scaling of the Fourier transform of the imaging system, the specific expression of the light field amplitude by the intensity filter unit 140 is: ; in, represents the amplitude transmission function of the intensity filtering unit 140; represents the wavelength of light emitted by the point light source 110 represents the focal length of the imaging unit 130; represents the horizontal spatial coordinate of the plane where the intensity filtering unit 140 is located; represents the longitudinal spatial coordinate of the plane where the intensity filtering unit 140 is located; After substituting into the calculation, refer to Figure 3 , The scale provides a size reference. It can be seen that the input letter A has an edge enhancement effect only along the x-direction, while the edge changing along the y-direction cannot be detected. Therefore, this method can be used to achieve edge detection in selective directions, which corresponds to differential imaging in the x-direction. Figure 4 , the horizontal axis is the spatial coordinate in micrometers, and the vertical axis is the normalized amplitude. A sharp peak appears at the coordinate, and the rest of the positions are close to 0, reflecting the optical intensity distribution at a specific position of the object, which is used to quantify the amplitude information of the original imaging.

[0038] At the same time, the results of second-order differential imaging in this system are also simulated. The specific expression of the light field amplitude by the intensity filter unit 140 is: ; in, represents the amplitude transmission function of the intensity filtering unit 140; represents the wavelength of light emitted by the point light source 110 represents the focal length of the imaging unit 130; represents the horizontal spatial coordinate of the plane where the intensity filtering unit 140 is located; represents the longitudinal spatial coordinate of the plane where the intensity filtering unit 140 is located; Substituting the intensity filter unit 140 into the Fresnel diffraction formula and performing calculations, the simulation results are as follows: Figure 5 As shown. Since the second-order differential imaging, i.e. the Laplace operation, is a symmetric filter, the boundaries in all directions can be highlighted. It can be seen that the result is consistent with the theory, all boundaries are detected, the intensity is concentrated in the area with gradient change of the input light field, and the intensity of the uniform area is suppressed. Figure 6 , the horizontal axis is micrometer coordinates, and the vertical axis is normalized intensity. There are multiple peaks on the curve (approximately The image shows the distribution of light intensity at different positions on the imaging surface 150 after differential modulation. Multiple peaks correspond to different edge positions of the closed pattern, indicating that the light intensity at the edge of the object is enhanced and the distinguishability is improved after differential processing. This quantitatively demonstrates the effect of the differential imaging system on extracting and enhancing object edge information.

[0039] Accordingly, the present invention also provides a method for preparing a differential imaging system, referring to Figure 7 ,include, Step S100, providing a point light source 110 for emitting light; Step S200 , providing an imaging unit 130 , which is disposed on the light-emitting side of the point light source 110 , for transmitting light to the imaging surface 150 ; In step S300, an intensity filter unit 140 is provided and disposed on a conjugate plane of the point light source 110 relative to the imaging unit 130. The intensity filter unit 140 has a set amplitude transmission function for differentially modulating the light output by the imaging unit 130 to obtain a modulated light field. The modulated light field forms a differential imaging light field on the imaging plane 150.

[0040] Specifically, the present invention can realize differential imaging in a single imaging process of a lens or objective lens, and has no plane wave restriction on the light source, and is applicable to a common point light source 110 optical path.

[0041] The architecture of this application can be directly integrated into a microscope system without changing the original structure of the microscope and is universally applicable to different types of microscopes. Specifically, the process involves placing a filter with a quadratic amplitude transmission function or a linear transmission function on a conjugate surface of the point light source 110 relative to the lens or objective imaging system. When the object distance and image distance satisfy the Gaussian imaging relationship, a differential imaging effect can be achieved during the objective lens's primary imaging process.

[0042] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0043] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A differential imaging system, characterized in that: include, Point light source, used to emit light; An imaging unit, provided on the light-emitting side of the point light source, for receiving and transmitting the light to an imaging surface; An intensity filtering unit is provided on a conjugate plane of the point light source relative to the imaging unit. The intensity filtering unit has a set functional amplitude and is used to differentially modulate the light output by the imaging unit to obtain a modulated light field. The modulated light field forms a differential imaging light field on the imaging plane.

2. The differential imaging system according to claim 1, characterized in that The intensity filter unit is a filter with a linear function amplitude, and the modulated light field is represented by the following expression: ； in, represents an arbitrary constant; 、 represent the spatial frequency components of the light in Fourier space respectively; represents the Fourier transform result of the light; represents Fourier transform; represents the first-order partial derivative of the light in the x direction.

3. The differential imaging system according to claim 1, wherein: The intensity filter unit is a filter with a quadratic function amplitude, and the modulated light field is represented by the following expression: ； in, represents an arbitrary constant; represents the sum of the squares of spatial frequencies; represents the Fourier transform result of the light; represents Fourier transform; represents the Laplacian of the ray.

4. The differential imaging system according to claim 1, wherein: The expression of the differential imaging light field is: ； in, represents the differential imaging light field; represents Fourier transform; represents the amplitude transmission function of the intensity filter unit; represents the light incident on the imaging unit; Indicates the secondary phase that does not affect the imaging results; represents the radial coordinate of the imaging plane; represents the distance from the image side principal plane in the imaging unit to the imaging surface; Represents the distance from the image principal plane in the imaging unit to the intensity filtering unit.

5. The differential imaging system according to claim 1, characterized in that The imaging unit includes a lens, an objective lens, or an optical imaging device based on the conjugate imaging principle.

6. The differential imaging system according to claim 1, characterized in that The conjugate condition of the plane where the point light source is located and the plane where the intensity filter unit is located is expressed by the following expression: ； in, represents the distance from the point light source to the principal plane of the image side in the imaging unit; represents the distance from the main plane of the image side in the imaging unit to the intensity filtering unit; represents the focal length of the imaging unit.

7. The differential imaging system according to claim 1, wherein: The conjugate condition between the imaging plane and the object plane where the sample is located is expressed by the following expression: ； in, represents the distance from the object plane to the principal plane of the image side in the imaging unit; represents the distance from the image side principal plane in the imaging unit to the imaging surface; represents the focal length of the imaging unit.

8. The differential imaging system according to claim 1, wherein: It also includes a light intensity capturing unit, which is used to capture the modulated light field after being filtered by the intensity filtering unit.

9. The differential imaging system according to claim 8, characterized in that: The light intensity capturing unit includes a charge coupled device sensor or a complementary metal oxide semiconductor sensor.

10. A method for preparing a differential imaging system, characterized in that: include, Provide a point light source for emitting light; Providing an imaging unit, which is arranged on the light-emitting side of the point light source and is used to propagate the light to an imaging surface; An intensity filtering unit is provided and arranged on a conjugate plane of the point light source relative to the imaging unit. The intensity filtering unit has a set amplitude transmission function and is used to differentially modulate the light output by the imaging unit to obtain a modulated light field. The modulated light field forms a differential imaging light field on the imaging plane.

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